1. Field of the Invention
The present invention relates generally to stepping motors and, more particularly, to a simple stepping motor for providing oscillating motion.
2. Background Art
Stepping motors are well known devices for producing incremental motion in which electrical pulses are translated into mechanical movements by causing an output shaft to move a specific incremental distance or "step" for each pulse applied to the motor. As opposed to a conventional motor which has a free-running shaft, the stepping motor shaft moves in fixed, repeatable known increments, resulting in the ability to accurately position. These motors are controlled by drive circuitry which provides the necessary number, sequence, and rate of pulses to achieve the desired extent of movement.
Conventional stepping motors have at least two stator phases. To take a step, the current is alternately changed (reversed), first in one phase, then in the other. Each change causes the rotor of the motor to rotate one step which may be 15 degrees 7.5 degrees 2 degrees or whatever step angle the motor has been designed to produce. In many applications, a very large number of pulses may be produced to cause the rotor to rotate a selected number of rotations in one direction.
Some applications, such as some bar code readers, require a stepping motor to take only one step clockwise and then one step counter-clockwise, thus producing an oscillating hack-and-forth motion. In the case of bar code readers, the oscillating motion sweeps a laser beam across the bar code so that the bar code can be "read" by means of decoding the pattern of reflected light.
A disadvantage of conventional stepping motors used in oscillating modes is that they are relatively more complicated than need be to produce the simple oscillating motion.
Accordingly, it is a principal object of the present invention to provide an oscillating stepping motor that is simple, has relatively few parts, and is economical to construct.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.